Python Tutorial

In this tutorial, we will discuss how to adjust the size of figures created with matplotlib in Python. Matplotlib library is widely used for creating graphs.

Introduction

Matplotlib is popular for creating figures for representing data. We can populate the figure with all different types of data, including axes, a graph plot, a geometric shape, etc. We can perform various operations on a matplotlib generated graph where adjusting the sizing is a common task. Sometimes, we require setting the size of the figure to a specific size. The graph can be wider in size, taller in height, etc.

The matplotlib. figure() provides the figsize attribute that specifies the width and height of a figure in-unit inches. Let's understand the following syntax.

Syntax:

import matplotlib.pyplot as plt
figure_name = plt.figure(figsize=(width, height))

The figsize is an optional parameter of figure() method. By default, the figure has the dimensions as (6.4, 4.8).

Generally, each unit inch is 80 x 80 pixels. However, we can change the pixel per unit inch using the dpi parameter, which can be specified in the same function.

We will follow the below approach.

We will define a variable val_1, and set it equal to plt.figure(figsize=(6,3)).
It will create a figure object with a width of 6 inches and 3 inches in height.
The figsize attribute has a value tuple of 2 values.

Let's understand the following example.

Example -

# We start by importing matplotlib
import matplotlib.pyplot as plt

# Plotting a figure of width 6 and height 3
plot_1 = plt.figure(figsize=(6, 3))

# Let's plot the equation y=2*x
x = [1, 2, 3, 4, 5, 6,7]

# y = [2,4,6,8,10, 12, 14]
y = [x*2 for x in x]

# plt.plot() specifies the arguments for x-axis
# and y-axis to be plotted
plt.plot(x, y)

# To show this figure object, we use the line,
# fig.show()
plt.show()

Output:

How to change the size of figure drawn with matplotlib?

Example - 2:

# importing matplotlib library
import matplotlib.pyplot as plt

# Now we plot a figure of width 7 and height 12
plt_1 = plt.figure(figsize=(2, 5))

# Using the equation y=3*x
x = [1, 2, 3, 4, 5]

# y = [3,8,27,64,125]
y = [x*2 for x in x]

# plt.plot() determines the arguments for
# x-axis and y-axis to be plotted
plt.plot(x, y)

# To show this figure object, we use the line,
# fig.show()
plt.show()

Output:

In the above code, we have increased the height as compare to width and changed the graph plot.

We can also set the size of the subplots using the same method. Let's understand the following example.

Example -

import matplotlib.pyplot as plt

fig, axes= plt.subplots(nrows=2, ncols=1,figsize=(8,4))

x= [1,2,3,4,5]

y=[x**3 for x in x]

axes[0].plot(x,y)
axes[1].plot(x,y)

plt.tight_layout()

plt.show()

Output:

Set the Height and Width of a Figure in Matplotlib

We can also set the figure's height and width without using the figsize argument. It can be done using the set() function with the figheight and figwidth arguments. The set_figheight() and set_figwidth() functions are also used to set height and width.

Let's understand the following example.

Example -

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(0, 20, 0.2)
y = np.sin(x)
z = np.cos(x)

fig = plt.figure()

fig.set_figheight(4)
fig.set_figwidth(8)

# Adds subplot on position 1
ax = fig.add_subplot(121)
# Adds subplot on position 2
ax2 = fig.add_subplot(122)

ax.plot(x, y)
ax2.plot(x, z)
plt.show()

Output:

On the other hand, we can also use the set_size_inches(). Below is the example.

Example - 2:

import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()

fig.set_size_inches(10, 5)

# Adds subplot on position 1
ax = fig.add_subplot(121)
# Adds subplot on position 2
ax2 = fig.add_subplot(122)

ax.plot(x, y)
ax2.plot(x, z)
plt.show()

Output:

Modifying the Graph

It is another way to modify the graph attributing without using the figure environment. We can also update matplotlib.rcParams, an instance of RcParams for handling default matplotlib values.

Let's understand the following example.

Example -

import matplotlib.pyplot as plt
plt.rcParams['figure.figsize'] = (6, 12)
x = y = range(2, 20)
plt.plot(x, y)
plt.show()

Output:

Conclusion

We have discussed several ways to change the size of a figure in matplotlib. These figures are very useful for data visualization. You can use any option that suit your requirement.

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